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Digital Aerial Photos

Two types of digital aerial photos are used within the programme - orthorectified and non-orthorectified.

Orthorectified aerial photography for the whole of the coast between Portland Bill and Beachley Point, including all major estuaries, was collected between 2006 and 2008. The remaining area between Sand Point and Beachley Point will be flown in 2009. The photography was all flown to 10cm resolution which is equivalent to 1:5000 scale film.

An example of a digital aerial photograph showing West Bay Harbour, Dorset

Orthorectified photos are generated using photogrammetrically based techniques; this requires the production of a good quality digital elevation model (DEM). This is derived from the LiDAR collected by the programme. The accuracy of the Lidar is such that the positional accuracy of the orthorectified photography is +/- 30cm.

Digital aerial photos offer tremendous advantages, when compared with ordinary contact prints, and with conventional large scale OS maps. When correctly georeferenced, the data sets can be used within GIS in combination with vector map data (typically from the OS) for many shoreline management applications. Digital images offer the following additional detail, relative to conventional large scale OS mapping:

 

• Geomorphological structure

• Geology

• Sediment type

• Saltmarsh morphology

• Land use

• Defence detail

• Beach plan shape

• Recent shoreline position

• Vegetation coverage

• Increased detail at large scale

• Evidence of nearshore sediment plumes

• Location of nearshore submerged sea bed features

 

Data is used for interpretation of geomorphological changes and assessment of coastal erosion and accretion. The data collected by the programme is also used in habitat mapping and water quality assessment.

 

As the photography is used for the habitat mapping programme the photos are collected between May and September, when vegetation is at its most abundant. Photography is also collected at low water on spring tides to cover as much of the beaches as possible.

 

For the purpose of water quality assessment false colour infrared images are taken of estuaries and certain other selected sites. These can be used to detect such features as algal blooms, which may effect water quality

An example of a FCIR Image of East Fleet

The orthorectified photography collected by the programme is freely available to view in the map viewer. Photos can be downloaded or simply visualised by zooming in to the area of interest. Downloaded photos can be imported to any GIS supporting ECW format files. This is recommended as the file format is fast to load. The files are very large but can easily be used in GIS and CAD systems.

Non-orthorectified aerial photography will be collected for the whole of the shoreline within the programme’s boundaries in the third year of the programme.